In general, as shown in FIG. 9, a chain or belt transmission device for valve timing in an internal combustion engine, or for transmitting rotational power in another drive mechanism, includes a chain or belt CH, which transmits power from a driving sprocket or pulley S1 to one or more driven sprockets or pulleys S2. The transmission includes a pivotally mounted, movable sliding contact guide Ga, which cooperates with a tensioner, and a fixed sliding contact guide Gb. The movable guide and the fixed guide are attached to a frame E of the engine or other drive mechanism by suitable pins P or by bolts, or similar mountings. The guides make sliding contact with the chain or belt CH, and prevent vibration of the chain or belt both in the plane of its traveling path (which is usually vertical), and in the transverse direction. The pivoting guide Ga cooperates with a tensioner T to maintain tension in the chain or belt.
FIG. 7, is an exploded side view of a movable guide (i.e., a tensioner lever) 30 for use with a chain, as disclosed in Japanese Patent No. 3253951. FIG. 8 is bottom plan view of the guide. The guide 30 comprises a guide body including a shoe 31 on a surface of which chain CH travels in sliding contact. A plate-receiving portion 32 is provided on a back of the shoe 31, and extends along the longitudinal direction of the guide. The plate-receiving portion and the shoe are integrally molded as a unit from a synthetic resin. A reinforcing plate 40, composed of a rigid material, is fitted into a slot 32a in an edge of the plate-receiving portion. This slot opens in a direction facing away from the shoe, and extends along the longitudinal direction of the guide. The plate-receiving portion 32 is provided with a mounting hole 32b adjacent one end thereof, for mounting the guide body on a frame of an engine, or other machine. A mounting hole 41 is provided adjacent one end of the reinforcing plate 32 at a position such that it comes into register with the mounting hole 32b when the reinforcing plate 40 is fitted into slot 32a. This allows the guide body and reinforcing plate to be fastened together on a pivot means such as a mounting bolt, a mounting pin or the like.
Since the shoe 31 and the plate-receiving portion 32 are integrally molded as a unit from a synthetic resin, it is not necessary to provide a separate shoe. Thus, the number of parts, and the number of production steps are reduced. Further, since the reinforcing plate 40 is received in slot 32a in the plate-receiving portion 32 the strength of the guide in its pivoting direction is increased, and its bending rigidity, toughness and strength are significantly improved. The use of this type of guide has increased rapidly due to the demand for low cost and high reliability.
However, in order to increase the strength of the guide, it is necessary to increase the thickness in the reinforcing plate. The increase in thickness results in an undesirable increase in the weight of the reinforcing plate and in the overall weight of the guide. Moreover, when reinforcing plates are formed by punching a rolled metallic sheet or by molding a fiber-reinforced resin, production difficulties are encountered when increased plate thickness is desired. Furthermore, some regions in the reinforcing plate require higher strength than others. For example the region surrounding the mounting hole, and the region adjacent the part that contacts the plunger of a tensioner, require higher strength than other regions. However, it was not easy to vary the strength of a conventional reinforcing plate to meet the requirements for added strength only in the regions where additional strength is needed. Accordingly, to meet these regional strength requirements, it was conventional practice to make the entire reinforcing plate thicker, and the result was an increase in the weight of the reinforcing plate and in the overall weight of the guide body.
Accordingly a general object of the invention is to solve one or more of the above-mentioned problems of conventional sliding contact guides. Another object of the invention is to provide a sliding contact guide having enhanced strength without increasing the weight guide. Still another object is to provide a simple way to control strength distribution in a guide, according to the strength requirements of respective regions of the guide body.